1. Field of the Invention
This invention pertains to voltage measuring devices for high-voltage installations, and particularly to voltage measuring devices employing electro-optical detection components.
2. Description of the Prior Art
Apparatus useful in measuring the voltage in an encapsulated high-voltage installation are described in United States patent application, Ser. No. 495,820, filed Aug. 8, 1974 and assigned to the same assignee as the present application. In general, the apparatus disclosed therein includes a capacitive voltage divider arrangement wherein the low voltage leg of the capacitor network is monitored by various devices to thereby give a reading which is proportional to the voltage between the inner conductor and the outer tube. Certain of the measuring devices described in the aforementioned application include electro-optical components such as the Kerr cell and the Pockels cell. The voltage developed across the "low voltage" capacitor of the capacitor voltage divider bridge is supplied to the electro-optical component with the result that the plane of polarization of polarized light entering the electro-optical component is shifted in proportion to said voltage.
Another utilization of an electro-optical component as a means for measuring voltage in such installations is described in German Offenlegungsschrift 2,130,046. Therein is described an electro-optical component which consists of an optical wave guide which is wound into a toroidal coil. The toroidal coil is mounted in a ring-shaped widening of the outer tube of the high-voltage installation. Since optical wave guides are relatively expensive, being more so when the latter are wound in toroidal coil form, the known device is a costly item to manufacture.
Further, it is known in the art that a Kerr of Pockels cell can be employed for the measurement of voltage, utilizing the electric field intensity (see the journal entitled "Elecktrie," vol. 22 (1968, No. 7, pages 261-266). However, this article does not indicate how an arrangement of a Kerr or Pockels cell can be employed in the extension of an outer tube of a high-voltage installation without adversely affecting the field pattern of the electric field between the inner conductor and the outer tube.
It is therefore a primary object of the invention to provide a measuring device for such high-voltage installations which can be manufactured at a relatively low cost.
It is a further object of this invention to provide a measuring device which employs electro-optical components positioned in the electric field between the conductors without adversely affecting the field lines.
It is another object of this invention, to employ electro-optical components in such a manner that the additional space required to house such components is kept to a minimum.